Generally, cushioning articles such as mattresses have an innercore formed from an array of helically shaped spring coils to provide mattress resiliency. Typically each spring coil is individually made of steel wire and then attached to other springs to form a matrix of rows and columns of springs in the size and shape desired. These types of spring assemblies may be used in mattresses, sofas, box springs, car seats and other types of furniture.
An alternative inner spring core uses leaf springs arranged in a matrix of rows. One example of a leaf spring innercore is described in U.S. Pat. No. 4,935,977 which shows a leaf spring assembly comprised of upwardly curved flat bar leaf springs designed to flex at various loads. The depicted leaf springs extend across the width of the mattress with attachment points at either side that hold the spring under tension. A sleeping user causes a downward force that compresses the leaf springs, causing them to flex downwardly and deform, increasing the tension in the spring. An additional leaf spring design is depicted in U.S. Pat. No. 6,170,808, which shows a sparse matrix of leaf springs cut from a metal plate and arranged into a mattress core. Each leaf spring is upwardly curved and covered with a foam support pad to thereby support a portion of the load of a sleeping user. Each spring is fixed at a center location. A downward force causes the spring to deform, compressing the spring downwardly. A transverse force may cause the spring to tilt about its point of attachment, deforming under the lever action of the cantilevered spring.
As noted in the above publications, the mechanical dynamics by which leaf springs carry a load has both similarities and differences with how coil springs carry a load, particularly a moving load, such as a person moving across a surface suspended by the spring elements. The dynamic response of a leaf spring has similarities and differences from that of a coil spring, and modeling those differences is challenging. As noted in “Automotive Math Handbook”, Forbes Air MBI Publishing Company (2000) pg. 81, the calculation of the rate of mono-leaf spring is challenging and any equation or model of rate is at best an approximation, requiring it be checked against empirical analysis. The response is further complicated by the restraining effect of lacing wires, border wires and fabric, all of which effect dynamics. As such, there remains a need in the art for a leaf spring assembly that provides improved load mechanics, including improved load carrying mechanics for a moving load or loads.